A miniaturized planar transistor is used in the broad sector of computers, communication equipment, instruments, automatic control devices, and machinery and tools used in daily life, as microprocessors, ASIC and microcomputers which have low power consumption, are low in cost and which have high information processing ability; and as low-cost high-capacity memory. With a planar type transistor, a source, gate, and drain are horizontally arranged relative to a silicon substrate surface. On the other hand, with an SGT, the source, gate and drain are arranged vertically relative to the silicon substrate. The gate incorporates a convex semiconductor layer arranged on a silicon substrate (for example, reference is made to non-patent literature 1, and to FIG. 94 of the specification of the present application). Furthermore, in comparison to a planar type transistor, the area possessed by the SGT is small relative to the substrate (for example, reference is made to non-patent literature 2).
For an SGT as well, as with the planar transistor, the realization of high-speed operation and low power consumption is sought. The SGT structure is greatly influenced by the creation process. With a typical SGT production method, an SGT silicon column is formed by etching the silicon layer by means of the dry etching method. The cross-sectional shape of an SGT silicon column thus formed by the characteristics and dry etching generally becomes a trapezoid (for example, reference is made to patent literature 1, and to FIG. 94 of the specification of the present application). Furthermore, with an SGT in which the cross-section of a silicon column is a trapezoid, the realization of high-speed operation and low power consumption is sought.    [Patent Literature 1] Unexamined Japanese Patent Application KOKAI Publication No. 2007-123415    [Non-Patent Literature 1] H. Takato. Et. al, IEEE Transactions on electron devices vol. 38, No. 3, March 1991, pp. 573-578    [Non-Patent Literature 2] S. Watanabe, IEEE Transactions on electron devices, vol. 50, October 2003, pp. 2073-2080